The invention relates to an open-end rotor spinning arrangement having a spinning rotor that has a shaft that is disposed in a wedge-shaped gap formed by two pairs of supporting disks. The shaft is supported in axial direction at a step bearing and is driven by a tangential belt. The shaft carries a rotor (rotor plate) that is surrounded by a rotor housing, and the supporting disks are disposed in a bearing block at which a step bearing housing of the step bearing is mounted. The shaft, with respect to the step bearing housing and the rotor housing, is sealed off by a sealing element.
In a known open-end rotor spinning arrangement, German Unexamined Patent Application DE-OS No. 28 33 134, relatively large dimensions are required in longitudinal direction of the shaft of the spinning rotor. In the case of this construction, a bearing block is provided that is delimited by two flanges between which the pairs of supporting disks are arranged. The supporting disks of the pairs of supporting disks are offset with respect to one another in axial direction so that a distance is obtained between the flanges that amounts to at least four times the width of the supporting disks plus the dimension of the tangential belt or of a tension roller stressing the tangential belt. In the case of the known construction, the bearing block is carried by a rotor housing to which one of the flanges is screwed. A step bearing housing is fastened at the other flange.
In another known construction, German Unexamined Patent Application DE-OS No. 32 47 411, the step bearing housing is fastened at the bearing block via arms that reach around the supporting disks in a fork-shaped way. The bearing block itself is held at parts of the machine frame. In this construction, the rotor housing is mounted at the machine frame independently of the bearing block.
An object of the invention is to provide an open-end rotor spinning arrangement of the initially mentioned type in such a way that it is suitable for very high rotational speeds of the rotor, without the necessity of enlarging the dimensions, particularly of the shaft of the spinning rotor.
This object is achieved by holding and centering the rotor housing directly at the bearing block that serves as the carrying element for the step bearing housing and the rotor housing.
This arrangement is based on the recognition that the critical rotational speed of the spinning rotor represents a significant limitation for the maximally possible rotational speed, and that this critical rotational speed can be increased without enlarging the diameter of the rotor shaft by developing the rotor shaft as short as possible. In order to achieve this short rotor shaft construction, a relatively short distance will exist between the rotor housing and the step bearing housing. Increasing critical rotational speed was discussed in commonly assigned U.S. patent application Ser. No. 909,945, filed Sept. 22, 1986, now U.S. Pat. No. 4,703,616, which addressed minimizing the distance between two pairs of supporting disks in an open-end spinning apparatus, including a braking element. U.S. patent application Ser. No. 909,945 is hereby incorporated by reference.
It is also provided that the effect of a vacuum existing in the rotor housing cannot extend into the area of the step bearing housing. Otherwise, lubricant that emerges from the step bearing housing in the form of mist or the like could be sucked into the rotor housing which would result in disturbances of the spinning process. Both the step bearing housing and the rotor housing are mounted directly at the bearing block of the supporting disks. Therefore, it is possible to provide sealing elements by which the rotor shaft is sealed off with respect to the step bearing housing and the rotor housing, with very narrow tolerances, because both parts are aligned and centered with respect to the bearing block.
In further advantageous features of certain preferred embodiments of the invention, it is provided that the step bearing housing is provided with a recess into which ring-shaped sealing elements are inserted that surround the shaft. In these embodiments, the sealing elements can be exchanged easily in the case of wear. In this case, it is also advantageous that, as a further development of the invention, at least one of the sealing elements is equipped with a sliding surface that surrounds the shaft at a narrow distance. This ensures that in the case of a possible wear of the coating of the supporting disks and a resulting shifting of the shaft, the latter can touch the sealing elements without destroying itself and/or the sealing elements.
In further advantageous features of certain preferred embodiments of the invention, it is provided that the bearing block is equipped with guiding elements on which the rotor housing is guided in vertical and horizontal direction. On these guiding elements, the rotor housing can be aligned very precisely. There is also the advantage of an easy mounting and demounting. In the case of certain advantageous embodiments, it is provided that the guiding elements have a web-type shape and extend in the direction of the rotor housing and in parallel to the shaft beyond the pair of supporting disks facing the rotor housing.
In further advantageous features of certain preferred embodiments of the invention, it is provided that the distance between the pairs of supporting disks in longitudinal direction of the shaft corresponds to about 0.65 to 0.85 times that a section length that the shaft has from the pair of supporting disks closest the rotor housing to the end of the shaft projecting into the step bearing housing.
Tests have shown that the critical rotational speed is largely independent of the contact pressure of the tangential belt and of the weight of the rotor and remains more or less constant, but depends very clearly on the distance of the supporting disks and the length of the shaft by which the shaft projects beyond the pair of supporting disks facing the step bearing housing. Tests show that probably an optimum with respect to the height of the critical rotational speed will exist when the mentioned ratio is about 0.75. In the case of a practical embodiment, particularly high critical rotational speeds were obtained, where the distance between the pairs of supporting disks amounts to about 50 mm, and the projection of the shaft, i.e., the length of the shaft from the pair of supporting disks facing the step bearing to its end, is 20 mm.
Other objects, advantages and novel features of the Present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.